Re: [R] How to solve differential equations with a delay (time lag)?
Hi,
I would like to add an additional piece of information to my previous
posting:
y[1](t) = 0, for all t in the interval (-delay, 0)
This completes the specification of the problem.
Thanks,
Ravi.
---
Ravi Varadhan, Ph.D.
Assistant Professor, The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email: [EMAIL PROTECTED]
Webpage: http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Ravi Varadhan
Sent: Wednesday, November 29, 2006 4:45 PM
To: r-help@stat.math.ethz.ch
Subject: [R] How to solve differential equations with a delay (time lag)?
Hi,
I would like to solve a system of coupled ordinary differential equations,
where there is a delay (time lag) term. I would like to use the lsoda
function odesolve package. However, I am not sure how to specify the
delay term using the syntax allowed by odesolve.
Here is an example of the kind of problem that I am trying to solve:
library(odesolve)
yprime - function(t, y, p) { # this function
yd1 - p[k1] *(t = p[T]) - p[k2] * y[2]
yd2 - p[k3] * y[1](t - p[delay]) - p[k4] * y[2] # this is not
syntactically valid, but it is what I would like to do
list(c(yd1,yd2))
}
times - seq(0,30,by=0.1)
y0 - c(0,0)
parms - c(k1=0.7, k2=0.5, k3=0.2, k4=0.8, T=10, delay=5)
Is there a way to incorporate delay in odesolve?
Any hints would be much appreciated.
Ravi.
---
Ravi Varadhan, Ph.D.
Assistant Professor, The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email: [EMAIL PROTECTED]
Webpage: http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html
[[alternative HTML version deleted]]
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] How to solve differential equations with a delay (time lag)?
lsoda does not solve delay differential equations, which is what you
need to be able to do. A quick search on netlib (netlib.org) turned up
one match for delay differential equations: ode/ddverk.f, which might
help (though not in R).
R. Woodrow Setzer, Ph. D.
National Center for Computational Toxicology
US Environmental Protection Agency
Mail Drop B205-01/US EPA/RTP, NC 27711
Ph: (919) 541-0128Fax: (919) 541-1194
Ravi Varadhan
[EMAIL PROTECTED]
eduTo
Sent by: r-help@stat.math.ethz.ch
[EMAIL PROTECTED]cc
tat.math.ethz.ch
Subject
[R] How to solve differential
11/29/2006 04:44 equations with a delay (time
PM lag)?
Hi,
I would like to solve a system of coupled ordinary differential
equations,
where there is a delay (time lag) term. I would like to use the lsoda
function odesolve package. However, I am not sure how to specify the
delay term using the syntax allowed by odesolve.
Here is an example of the kind of problem that I am trying to solve:
library(odesolve)
yprime - function(t, y, p) { # this function
yd1 - p[k1] *(t = p[T]) - p[k2] * y[2]
yd2 - p[k3] * y[1](t - p[delay]) - p[k4] * y[2] # this is not
syntactically valid, but it is what I would like to do
list(c(yd1,yd2))
}
times - seq(0,30,by=0.1)
y0 - c(0,0)
parms - c(k1=0.7, k2=0.5, k3=0.2, k4=0.8, T=10, delay=5)
Is there a way to incorporate delay in odesolve?
Any hints would be much appreciated.
Ravi.
---
Ravi Varadhan, Ph.D.
Assistant Professor, The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email: [EMAIL PROTECTED]
Webpage:
http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html
[[alternative HTML version deleted]]
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] How to solve differential equations with a delay (time lag)?
Thanks, Woodrow. I also found a DDE solver called dde23 in Matlab written
by L.F. Shampine. I will see if I can use it in Scilab, since I don't have
Matlab.
Ravi.
---
Ravi Varadhan, Ph.D.
Assistant Professor, The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email: [EMAIL PROTECTED]
Webpage: http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Wednesday, November 29, 2006 5:26 PM
To: Ravi Varadhan
Cc: r-help@stat.math.ethz.ch
Subject: Re: [R] How to solve differential equations with a delay (time
lag)?
lsoda does not solve delay differential equations, which is what you
need to be able to do. A quick search on netlib (netlib.org) turned up
one match for delay differential equations: ode/ddverk.f, which might
help (though not in R).
R. Woodrow Setzer, Ph. D.
National Center for Computational Toxicology
US Environmental Protection Agency
Mail Drop B205-01/US EPA/RTP, NC 27711
Ph: (919) 541-0128Fax: (919) 541-1194
Ravi Varadhan
[EMAIL PROTECTED]
eduTo
Sent by: r-help@stat.math.ethz.ch
[EMAIL PROTECTED]cc
tat.math.ethz.ch
Subject
[R] How to solve differential
11/29/2006 04:44 equations with a delay (time
PM lag)?
Hi,
I would like to solve a system of coupled ordinary differential
equations,
where there is a delay (time lag) term. I would like to use the lsoda
function odesolve package. However, I am not sure how to specify the
delay term using the syntax allowed by odesolve.
Here is an example of the kind of problem that I am trying to solve:
library(odesolve)
yprime - function(t, y, p) { # this function
yd1 - p[k1] *(t = p[T]) - p[k2] * y[2]
yd2 - p[k3] * y[1](t - p[delay]) - p[k4] * y[2] # this is not
syntactically valid, but it is what I would like to do
list(c(yd1,yd2))
}
times - seq(0,30,by=0.1)
y0 - c(0,0)
parms - c(k1=0.7, k2=0.5, k3=0.2, k4=0.8, T=10, delay=5)
Is there a way to incorporate delay in odesolve?
Any hints would be much appreciated.
Ravi.
---
Ravi Varadhan, Ph.D.
Assistant Professor, The Center on Aging and Health
Division of Geriatric Medicine and Gerontology
Johns Hopkins University
Ph: (410) 502-2619
Fax: (410) 614-9625
Email: [EMAIL PROTECTED]
Webpage:
http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html
[[alternative HTML version deleted]]
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
